Solid-state laser oscillator with gain media in active mirror configuration

Abstract

An apparatus and method for achieving a near diffraction-limited, high-average power output from a solid-state laser oscillator are provided. The solid-state laser uses multiple disk-shaped laser gain media having a large optical aperture placed in an unstable resonator. The laser gain media is provided with optical coatings for operation in the active mirror configuration and is attached to a rigid, cooled substrate, which allows it to maintain a prescribed shape even when experiencing significant thermal load. The resonator is configured so as to preferentially support low order optical modes with transverse dimensions sufficiently large to efficiently fill the gain media apertures. Resonator configurations capable of producing standing wave or traveling wave optical fields are disclosed. The resonator may include means for intracavity correction of an optical phase front by adaptive optics. Also disclosed is an arrangement of resonator gain elements in axisymmetric arrays suitable for integration into a compact and lightweight laser system.

In the claims:  
     
       1. A laser oscillator comprising: 
       a linear unstable optical resonator formed by a plurality of at least partially reflecting elements, said linear unstable optical resonator being suitable for recirculating laser radiation at a cavity wavelength to establish a cavity mode;  
       a plurality of active mirror amplifiers (AMA) modules arranged in spaced apart relation to one another and in operating relationship with said linear unstable resonator for providing laser amplification of said laser radiation at the cavity wavelength;  
       said plurality of AMA modules being arranged such that said laser radiation recirculating inside said resonator can be received, amplified, and retransmitted successively by each said AMA module;  
       each of said AMA modules including at least one, actively cooled solid-state laser gain medium arranged in an active mirror configuration, for supporting said laser gain medium and a pump for providing optical pump radiation into said laser gain medium for excitation thereof; and  
       said linear unstable optical resonator being operable to outcouple a portion of said laser radiation recirculating therein.  
     
     
       2. The solid-state laser oscillator of  claim 1  wherein said linear unstable optical resonator comprises a positive branch type laser oscillator. 
     
     
       3. The solid-state laser oscillator of  claim 1 , wherein said linear unstable optical resonator comprises a negative branch type laser oscillator. 
     
     
       4. The solid-state laser oscillator of  claim 1 , wherein said laser radiation recirculating inside said resonator substantially fills an optical aperture of each of said AMA modules. 
     
     
       5. The solid-state laser oscillator of  claim 1 , further including means for spectral filtering of said laser radiation. 
     
     
       6. The solid-state laser oscillator of  claim 5 , wherein said means for spectral filtering comprises an optical grating forming a part of the resonator, said grating being mounted to rotate so as to achieve wavelength selection of said laser radiation. 
     
     
       7. The solid-state laser oscillator of  claim 1 , further incorporating adaptive optics means within said unstable optical resonator to perform at least partial wavefront correction of optical radiation therein. 
     
     
       8. The solid-state laser oscillator of  claim 7  wherein: 
       said adaptive optics means includes at least one element for phase front correction, said one element being selected from one of a deformable mirror and a steering mirror,  
       said adaptive optics means including at least one sensor element, said sensor element comprising one of a wavefront sensor, a beam intensity profile sensor, and a sensor for measuring total laser beam power in a specified optical aperture.  
     
     
       9. The solid-state laser oscillator of  claim 1 , wherein said outcoupling function is provided by a partially transmissive element. 
     
     
       10. The solid-state laser oscillator of  claim 1 , wherein said plurality of AMA modules is arranged in first and second generally groups of circular arrays having approximately the same diameter; 
       said arrays being disposed in facing relationship and having a common axis of symmetry; and  
       said laser radiation being successively received, amplified and retransmitted alternately by said AMA modules in the first said array and the second said array.  
     
     
       11. A laser oscillator comprising: 
       a ring unstable optical resonator formed by a plurality of at least partially reflecting elements, said resonator being operable to recirculate laser radiation at a cavity wavelength to establish a cavity mode;  
       a plurality of active mirror amplifier (AMA) modules arranged inside said ring unstable optical resonator for providing laser amplification of said laser radiation at the cavity wavelength;  
       said plurality of AMA modules being arranged to allow laser radiation recirculating inside said resonator to be received, amplified and retransmitted successively by each said AMA module;  
       each said AMA module including:  
       at least one solid-state laser gain medium provided in an active mirror configuration,  
       a support for supporting said laser gain medium;  
       an optical pump for providing optical pump radiation into said laser gain medium for excitation thereof; and  
       said ring unstable optical resonator having a system for outcoupling a portion of said laser radiation recirculating therein from said resonator.  
     
     
       12. The solid-state laser oscillator of  claim 11 , wherein said ring unstable optical resonator comprises a positive branch type laser oscillator. 
     
     
       13. The solid-state laser oscillator of  claim 11 , wherein said ring unstable optical resonator comprises a negative branch type laser resonator. 
     
     
       14. The solid-state laser oscillator of  claim 13 , wherein said resonator further comprises a self-imaging type resonator. 
     
     
       15. The solid-state laser oscillator of  claim 11 , further incorporating a system for suppressing reverse wave oscillations in said ring unstable optical resonator. 
     
     
       16. The solid-state laser oscillator of  claim 11 , wherein said laser radiation recirculating inside said resonator substantially fills an optical aperture of each of said AMA modules. 
     
     
       17. The solid-state laser oscillator of  claim 11 , further including means for spectral filtering of said laser radiation. 
     
     
       18. The solid-state laser oscillator of  claim 17 , wherein said means for spectral filtering comprises an optical grating which forms a part of said resonator, said grating being mounted for radiation to enable wavelength selection of said laser radiation. 
     
     
       19. The solid-state laser oscillator of  claim 11 , further including adaptive optics means disposed within said unstable optical resonator to perform at least partial wavefront correction of optical radiation circulating therein. 
     
     
       20. The solid-state laser oscillator of  claim 19  wherein: 
       said adaptive optics means includes at least one of a deformable mirror or a steering mirror for performing phase front correction; and  
       said adaptive optics means including at least one of a wavefront sensor, a beam intensity profile sensor or a sensor for measuring total laser beam power in a specified optical aperture.  
     
     
       21. The solid-state laser oscillator of  claim 11 , wherein said outcoupling means include at least one partially transmissive element. 
     
     
       22. The solid-state laser oscillator of  claim 11 , wherein said plurality of AMA modules is arranged in two groups of generally circular arrays of approximately the same diameter size; 
       said arrays being disposed in facing relationship and having a common axis of symmetry; and  
       said laser radiation being successively received, amplified and retransmitted alternately by AMA modules in the first said array and the second said array.